Submission #301913

#	Time	Username	Problem	Language	Result	Execution time	Memory
301913		milisav	Monochrome Points (JOI20_monochrome)	C++14	100 / 100	767 ms	5640 KiB

monochrome

#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#define maxn 1000000
using namespace std;
int n;
long long ans=0;
char s[2*maxn];
int d[2*maxn];
int bit[8*maxn];
void update(int p,int v) {
    while(p<=2*n) {
        bit[p]+=v;
        p+=(p&(-p));
    }
}
int query(int p) {
    int ret=0;
    while(p>0) {
        ret+=bit[p];
        p-=(p&(-p));
    }
    return ret;
}
int l[maxn];
int r[maxn];
long long val(int i) {
    int cb=0;
    int x=0;
    int y=0;
    long long cans=0;
    int tmp=0;
    while(cb<i || s[y]!='B') {
        if(s[y]=='B') cb++;
        y++;
        if(y==2*n) y=0;
    }
    int k=1;
    l[k]=x;
    r[k]=y;
    d[x]=-k;
    d[y]=k;
    x++;
    while(x<2*n) {
        if(s[x]=='W') {
        k++;
        do {
            y++;
            if(y==2*n) y=0;
        } while(s[y]!='B');
            l[k]=min(x,y);
            r[k]=max(x,y);
            d[min(x,y)]=-k;
            d[max(x,y)]=k;
        }
        x++;
    }
    for(int i=0;i<2*n;i++) {
        if(d[i]>0) {
            update(l[d[i]]+1,-1);
            cans+=query(r[d[i]]+1)-query(l[d[i]]+1);
        }
        else update(i+1,1);
    }
    return cans;
}
int main() {
    scanf("%d",&n);
    scanf("%s",s);
    if(s[0]=='B') {
        for(int i=0;i<2*n;i++) {
            if(s[i]=='B') s[i]='W';
            else s[i]='B';
        }
    }

    int l=0,r=n-1;
    while(l<r) {
        int m1=(l+r)>>1;
        int m2=m1+1;
        long long v1=val(m1);
        long long v2=val(m2);
        ans=max(ans,v1);
        ans=max(ans,v2);
        if(v1>v2) r=m2-1;
        else l=m1+1;
    }
    ans=max(ans,val(l));
    printf("%lld",ans);
    return 0;
}

Compilation message (stderr)

monochrome.cpp: In function 'long long int val(int)':
monochrome.cpp:31:9: warning: unused variable 'tmp' [-Wunused-variable]
   31 |     int tmp=0;
      |         ^~~
monochrome.cpp: In function 'int main()':
monochrome.cpp:67:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   67 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
monochrome.cpp:68:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   68 |     scanf("%s",s);
      |     ~~~~~^~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 21 / 21
• Subtask 3: 10 / 10
• Subtask 4: 65 / 65